A Study of the Thread and Event Concurrency Models for Web Servers.pdf

A Study of the Thread and Event Concurrency Models for Web Servers Borys Bradel Catalin Drula Electrical and Computer Engineering Computer Science University of Toronto University of Toronto bradel@eecg.utoronto.ca catalin@cs.utoronto.ca 1. INTRODUCTION a thread is not executing. On the other hand the informa- Modern hardware for servers is capable of handling tens tion for events must be manually created and passed to the or hundreds of thousands of simultaneous Internet connec- controller so that it is maintained until the next event is exe- tions. Designing software that can handle such heavy loads cuted. The automatic approach has a higher space overhead requires concurrency. A program that performs tasks se- but the manual approach is harder to implement. Threads quentially is unnecessarily slow because it does not utilize are also harder to schedule effectively. When using threads the hardware resources effectively. The two main program- the thread system schedules the threads and the application ming models that enable programmers to write concurrent has little control over how this happens. When using events, programs are the thread-based and event-driven models. We on the other hand, the controller is part of the application will examine and compare the performance and ease-of-use and scheduling can therefore be done effectively. of the two models, in particular